I worked on new theme for the backend, It still
in progress but what is done is much more what is to be done.
This module (Inshas backend theme) is fully responsive, fully
compatible with all odoo views, and view inheritance, and of
course adds no overhead on rendering the views on client side
but also doesn't speed the rendering up.
It's as any module can be installed and uninstalled with no
side effects on other modules (except the ones depends on it
of course).
The theme is planed to be released in 15 days.

These screenshots demonstrate the views in "Done"
status:

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The following images demonstrate the responsiveness(Still
has little problems in re-positioning some elements):

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Following images demonstrate the views in (In Progress)
status:

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I also intend to test it on many devices after
publishing it as a demo on an online server also to allow
anyone intend to buy it to test it online. I started over
a month ago but didn't announce it because I wasn't sure
that I can reach so far, It was little bit complicated to
do this.
The Inshas theme will be available on Odoo app store
and/or private website or if I had a good deal to sell it
one time as a perpetual license I will sell it.